1. Field of the Invention
This invention concerns a mold tooling system for thermoforming molds used in molding a plastic web by vacuum forming or pressure forming parts of the web.
2. Description of the Prior Art
In conventional thermoforming machines for molding plastic webs or sheets, it is necessary to install a mold base of particular size and a molding assist box of corresponding size to cooperate with the mold base. The mold base provides a support for a mold of corresponding size. The mold base acts as a heat sink to draw heat from the mold which is continuously receiving heat from the heated plastic web. The mold base contains internal passages through which water passes to maintain the mold at predetermined molding temperature. Vacuum may be applied to the mold and plastic web through ports in the mold base, or gas pressure can be applied through a port in the molding assist box. Installation of a mold base, mold and molding assist box for molding parts of a web requires considerable costly setup time of highly skilled mechanics. For each different size mold, a mold base and molding assist box of corresponding size must be installed. For each thermoforming machine used for different size molds, it is necessary to stock a number of different mold bases and molding assist boxes of different sizes. These items are quite expensive, and as mentioned above, the labor cost of installation is high, and requires highly skilled mechanics.